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[Killietalk] K. marmoratus habitats, etc.
Mr. Robles's note raises some interesting questions. In terms of labeling
collection sites, generally, something like "R2007-1 (PuertoRico)" works well.
It is important to publish the locality in as much detail as possible. My
colleagues and I believe we have a good general idea of the ecology of Kmar,
but documenting new localities remains important, particularly in places where
the species is little known.
Several previous collections of kmar have been made in Puerto Rico. I made one,
quite casually, in the summer of 1967 in a coastal mangrove forest very near
Aguadilla on the west coast. This locality remains vivid in my mind, even
though the collection was made so long ago, because I remember collecting with
a dipnet right under trees that were heavily populated by monkeys. Large
aggregates of monkey feces in the water seemed to attract the fish. In the
midst of collecting, my companion and I realized that the monkeys were pelting
us with feces as well, and we had to take time out to bang the poles of our
nets against the trees in an effort to drive the monkeys away. I have, of
course, since been pelted with a fair share of the virtual feces that life
throws at us, but, so far as I can remember, this was the only time I was
actually pelted with REAL feces!
My colleagues and I tend to think of kmar as basically a marine animal. It is
extremely euryhaline, can tolerate much higher salinity than sea water, and
can jump from sea water into distilled water and survive. In my hands, in the
lab, it is hardier and more prolific in sea water (I use 35 ppt) and does not
breed very well (comparatively speaking) in freshwater. This is true of stocks
I have maintained from Florida, the Bahamas, Belize, Panama and Brazil. This
does not mean that it is not sometimes found in freshwater habitats. Sometimes
coastal mangrove forests get flooded by rain. For example, on the Belize
mainland, near Dangriga, we found an extensive mangrove forest
not 100 yards from the sea, where kmar was extremely abundant. To my surprise,
the water was virtually fresh, apparently due to recent rains. It was so fresh
that we took large numbers of Rivulus tenuis (generally a freshwater species) in
the same crab holes as the kmar. Mosquito larvae were super-abundant. But most
of the places we have taken it are clearly marine. For reasons i do not
understand, aquarists seem to have a hard time with this idea, and keep trying
to make kmar into a freshwater animal. This strikes me as pointless.
There are three other situations in which aquarists tend to uncritically force
their (valid) experience with other killifish species onto the biology of kmar:
1. Often, people try to collect it with seines. Experience has taught us that
animals taken in seines are those few that are not then occupying crab holes or
other fossorial habitats. Collecting inside crab holes, either with a small
dipnet or with a very tiny hook (barb removed) baited with a tiny worm or an
insect, is usually a great deal more productive. Small, hand made Gee traps
(i.e. funnel traps) inserted into crab holes and left there over a tidal cycle
also work very well. If you use this method, make sure that the crab has left;
otherwise it will push the trap out of the hole. Kmar are adept at leaving the
water to flip over the moist substrate, and, in places where they are abundant,
they can literally be taken by leaving a trap on the substrate, completely out
of water, overnight. Some of the largest animals I have ever seen have been
caught in this way. In general, the last place to look for this species is
2. Often, people try to breed it with ordinary spawning mops. It will place
its eggs on these mops, but then it will usually turn around and eat them. The
"false bottom" method works much better. My colleagues and I are nonplussed at
how many times we have to explain this. Spawning mops are the least efficient
way of breeding this species that we know of.
3. Often, people try to keep several hermaphrodites in the same small spawning
tank. This is a recipe for ending up with dead hermaphrodites. In confined
spaces, they are very aggressive, and they will kill one another. Sometimes, if
a male has been collected or appears in a laboratory stock, people will try to
pair it with a hermaphrodite in a small bowl or tiny breeding tank, on the
presumption that the hermaphrodite will immediately allow the male to mate with
it and cross fertilize some eggs. Bad idea! The sweet, innocent, female-like
"herm" will kill the male, and will do so at a frequency of about 90%. In
dealing with herms in general, it is a good idea to remember that they have
testicular tissue, and therefore androgens, and therefore the potential for
some male behaviors that really aren't very nice... Most hermaphrodites are
simply thugs to one another and especially to males.
Some weeks ago, there were press reports that kmar "lives in trees." Those
press reports were based on an article that my colleagues and I have in press:
"A Novel Terrestrial Fish Habitat inside Emergent Logs. This article will
appear in the Jan or Feb 08 issue of the American Naturalist. The abstract of
this article (authors: Taylor, D.S., Turner, B.J., Davis, WP and Chapman, B.)
reads as follows:
"Reports of new habitats for a major group of organisms are rare. Fishes display
diverse adaptations for temporary (amphibious) existence on land, but to our
knowledge, none have ever been reported regularly living inside emergent logs.
Here, we show that the mangrove killifish, Kryptolebias marmoratus, a species
previously known to emerse (leave the water) regularly, is now known to emerse
and aggregate in large numbers inside decaying mangrove logs that have been
?galleried? by terrestrial insects. This behavior has now been documented in
both Belize, Central America, and Florida, U.S.A., populations and represents
the first known case of fishes entering terrestrial woody material. The dense
packing of fish in the narrow log galleries may imply a novel social context in
which intraspecific aggressive behaviors are reduced, possibly mediated by the
physiological limitations imposed within this restrictive habitat."
The emergent logs referred to in the above abstract are almost entirely out of
water. We're not kidding here: split open the right log, an 50 or more animals
can be easily spooned out of the termite galleries. We now suspect that the
galleried logs might be the real "foci" for kmar populations. That is, in
general, we think that the "average" kmar individual will usually be found in
one of these logs. Logs should be searched at every opportunity.
should not be overlooked.
Bruce J. Turner
Dept. Biol. Sci.
Blacksburg, VA 24061
"...We are Hokies. We will prevail..."
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